# OpenAI vs Mistral AI

> OpenAI sells the widest closed-model platform with 1.05M context. Mistral undercuts it with open weights that run on its API, major clouds or your own GPUs.

Canonical: https://www.subconscious.dev/compare/openai-vs-mistral-ai · By The Subconscious Team · Updated September 30, 2026

## How they compare

OpenAI's lineup runs from GPT-6 Astra at $10 in and $50 out down to GPT-5.6 Luna at $0.20 in and $1.20 out, all with a 1.05M context and up to 128K output. Mistral's range is narrower and cheaper at the top: Medium 3.5 costs $1.50 in and $7.50 out and scores 77.6% on SWE-Bench Verified by Mistral's count, Large 3 costs $0.50 in and $1.50 out, and Small 4 costs $0.15 in and $0.60 out. Both discount heavily. OpenAI bills cached input at 10% of list and halves Batch; Mistral halves Batch and cuts cached input by up to 90%. Context is where OpenAI pulls ahead, with 1.05M against Mistral's 256K, though OpenAI doubles input rates past 272K.

The platforms differ more than the prices. OpenAI's Responses API bundles web search, file search, code execution, computer use and MCP, and the Agents SDK adds handoffs, guardrails and tracing. GPT-6 Astra posts frontier results on computer use. Mistral offers an Agents API with built-in tools, Codestral for code completion, OCR and Voxtral speech, but its bigger advantage is control. Its flagship weights are open, Medium 3.5 self-hosts on four GPUs, and EU or US regional endpoints serve data residency needs. OpenAI ships open gpt-oss models, but its best models stay closed, served direct, through Azure OpenAI or Bedrock. Mistral retires models quickly, so plan for migrations.

## What each one does

### OpenAI

OpenAI runs the most widely adopted closed-model API. Its September 2026 lineup has GPT-6 Astra at the top for computer use, coding and long agentic runs, priced at $10 in and $50 out per million tokens. Below it sits the GPT-5.6 family: Sol for hard professional work, Terra as the balanced default, and Luna for high-volume jobs at $0.20 in and $1.20 out. All of them carry a 1.05M token context window with up to 128K output.

### Mistral AI

Mistral AI is a Paris lab that sells its models through La Plateforme, its own API, and releases most of them as open weights. It consolidated the lineup in 2026. Mistral Medium 3.5, released April 28, is a dense 128B model that merges instruction following, reasoning and coding into one set of weights, and it replaced both Devstral 2 and the Magistral reasoning models. It costs $1.50 in and $7.50 out per million tokens and scores 77.6% on SWE-Bench Verified by Mistral's count. Mistral Small 4, a 119B mixture-of-experts model with 6.5B active, costs $0.15 in and $0.60 out. Mistral Large 3, a 675B MoE under Apache 2.0, runs $0.50 in and $1.50 out. All three carry a 256K context window.

## Which is best, and when

### Choose OpenAI for

- Frontier computer use and browser automation on GPT-6 Astra
- Hosted web search and file search in one API
- Prompts that need more than 256K of context

### Choose Mistral AI for

- Self-hosting the same model you prototyped on the API
- EU-region processing for residency requirements
- Mid-priced coding agents on Medium 3.5

## At a glance

| Attribute | OpenAI | Mistral AI |
|---|---|---|
| Model access | Closed, plus open gpt-oss | Open weights, plus closed Codestral |
| Flagship models | GPT-6 Astra, GPT-5.6 Sol, Terra, Luna | Mistral Medium 3.5, Small 4, Large 3 |
| Speed | Fast mode: up to 2.5x at 2x price | - |
| Price | $0.20–$10 in, $1.20–$50 out per 1M | $0.15–$1.50 in, $0.60–$7.50 out per 1M |
| Customization | N/A | Forge (enterprise); fine-tuning API deprecated |
| Deployment | API, Azure OpenAI, Bedrock | API, Azure, Bedrock, Vertex, self-host |
| Long context | 1.05M; 2x input past 272K | 256K |

## FAQ

### What is the difference between OpenAI and Mistral AI?

OpenAI sells the widest closed-model platform with 1.05M context. Mistral undercuts it with open weights that run on its API, major clouds or your own GPUs.

### When should I choose OpenAI over Mistral AI?

Frontier computer use and browser automation on GPT-6 Astra; Hosted web search and file search in one API; Prompts that need more than 256K of context.

### When should I choose Mistral AI over OpenAI?

Self-hosting the same model you prototyped on the API; EU-region processing for residency requirements; Mid-priced coding agents on Medium 3.5.

### Is OpenAI or Mistral AI cheaper?

OpenAI: $0.20–$10 in, $1.20–$50 out per 1M. Mistral AI: $0.15–$1.50 in, $0.60–$7.50 out per 1M. The cheaper choice depends on the model and workload.

### Which has more context, OpenAI or Mistral AI?

OpenAI: 1.05M; 2x input past 272K. Mistral AI: 256K.

## Running long-horizon agents?

If your agents run past 200K tokens, compare both against Subconscious: [Subconscious vs OpenAI](https://www.subconscious.dev/compare/subconscious-vs-openai.md), [Subconscious vs Mistral AI](https://www.subconscious.dev/compare/subconscious-vs-mistral-ai.md).

Full profiles: [OpenAI](https://www.subconscious.dev/providers/openai.md), [Mistral AI](https://www.subconscious.dev/providers/mistral-ai.md).